The present invention relates to an access checking system, i.e. a system making it possible to initiate an action equivalent to an authorisation following the checking of the identity of an object introduced into said system.
To a certain extent the system according to the invention constitutes a "key-lock" system, provided that these terms are given a broad sense. The word "key" must be understood to designate a support object provided with an identity and the word "lock" is understood to mean a member able to recognise the identity in question and control an action. However, the support object according to the invention is not necessarily in the traditional form of a key. It can have a random shape and can in particular be a card. With respect to the "control member" function, it is not necessarily limited to the action on the latch or bolt of a door, but can correspond to an access authorisation to a random data processing, telematic, bank or similar system. However, in order to show the originality and essential features of the invention, the variant of the system assuming the form of the traditional "key-lock" system will be used as a basis, but without this example having any limitative character.
The very principle of the lock mechanism is to give a portable object (the key) an identity (e.g. a profile) and to provide a member (the lock) able to recognise this identity and initiate an action. According to this known principle, the key is a reproducible object, because obviously several people must be able to have the same key (the members of one family, the same company, etc.). As the lock is linked with the special form given to the key, it can only cooperate with a single type of key.
Recently more sophisticated systems have appeared and these can be designated by the generic term of "electronic locks". In such systems, the identity is translated into a code written on an optical or magnetic track, which is placed on a type of credit card. However, the philosophy of the system remains the same, each key (in the present case each card) being reproducible. However, as in such improved systems the identity information is of a numerical and no longer a mechanical nature, it is possible to record several different identities in an electronic memory. Several different keys are then able to open the same lock. These keys can be allocated to different authorised persons, but can also be used by maintenance or security services.
In such systems, several digital words are written into a random access memory, which to a certain extent acts as a reference and these same words are written on to several cards. When one of these cards is introduced into a card reader, the code written on the card is detected and the resulting digital signal is compared with various reference words written in the memory. A comparitor establishes whether or not coincidence exists between the read word and one of the stored words. In the affirmative, a signal is emitted for controlling a random action, e.g. the opening of a catch.
For example, such a system is described in French patents Nos. 2 107 529, 2 325 992, 2 457 524 and 2 533 340.
Although satisfactory in certain respects, these systems suffer from a major disadvantage linked with the absence of confidentiality of the code carried by the card. Thus, it is easy to read the code inscribed on a stolen card and to re-write said code on a new card. In other words there is a real risk of fraudulent duplication of the support.
The object of the invention is to obviate this disadvantage. This is achieved through the use of a key which, by its very nature, is not reproducible. This characteristic is obtained by choosing as the information able to define the identity of a key a natural information constituted by the texture of the surface of a member and not information artificially produced (such as a tooth system or a magnetic or optical property of a strip). This information is of a complexity such that it is not reproducible. In addition, said information is unique, because even two objects which are identical in the macroscopic sense are in reality different on descending to the level of their surface texture. There is obviously no reason why an artificial texture should not be added to the natural texture in the form of scratches, streaks, marks, etc.
The idea of using the texture of a surface as the identification means for certain objects is not new. The article by B. C. D'Agraives et al entitled "Surface Topography, a remarkable method for the identification of seals or structures in general", published in "Proceedings of the 3rd Esarda Symposium on Safeguards and Nuclear Material Management", Karlsruhe, Federal Republic of Germany, 6/8.5.1981, already describes the properties and interest of surface textures. This teaching also appears in British patent application No. 2 097 979 published on 10.11.1982 in the name of the European Atomic Energy Community (EURATOM) and entitled "Utilisation of surface textures as a random marking or unique identity".
The present invention takes up this idea again by applying it to the field of access checking systems.
The choice of the surface texture as an information source for the marking of key runs counted to all the aforementioned known principles because, by its very nature, said information is not reproducible. Thus, unlike in the past, the lock is no longer designed to recognise a predetermined information, because a texture is a virtually random magnitude and is consequently unforeseeable. Thus, it is no longer possible to load the memory of the lock with an information which has been determined beforehand, as was the case with the Prior Art systems. It is pointed out in this connection that in conventional electronic locks and as described in particular in French patent No. 2 325 992, loading takes place with the aid of a special card, which carries programming information relative to the lock. This information consists of lists of codes to be accepted and lists of codes to be refused. This programming card is introduced into the reader, which identifies it as such and which is designed so as to modify the list of stored codes.
This known system is still subject to a fraud risk, because it is possible to falsify the programming card by giving it forged codes. Thus, the lock can be controlled by cards carrying these forged codes.
The choice of the surface texture as the identification means makes it necessary to modify the authorised information loading procedure, so that it is impossible to forge or counterfeit the same. To this end, the lock according to the invention which, like electronic locks, is provided with different memory locations is such that these locations can only receive the reference information by reading keys which are authorised to open the lock. In other words, an information written on a support is no longer written into the lock memory. The reverse order is used according to the invention, i.e. keys are produced with a random texture and the locks are subsequently conditioned as a function of said keys.
According to the invention, the quantity used for identifying the key is a continuous analog quantity and is no longer a digital value. Thus, an analog procedure could optionally be adopted for the comparison operation between the reference quantity and the read quantity. However, it is natural that preference is given to the conversion of the analog signal into digital form, followed by digital processing.
Another original feature of the lock according to the invention is that the means responsible for reading the information contained in the support supplied thereto is a texture reader and no longer a magnetic reader.
It is pointed out that the advantages of the system according to the invention are not acquired to the detriment of the possibilities of conventional electronic systems which are entirely retained, i.e. temporary validation of a key, centralised management of a system of locks, counting the number of interventions of a particular key, etc.